What is Gold Used for in PCB Fabrication?
Businesses and consumers alike rely on electronic devices for nearly every aspect of day-to-day life. Automobiles are packed full of printed circuit boards (PCBs) for everything from lighting and entertainment to sensors that control the behavior of critical mechanical functions. Computers, tablets, smartphones, and even many toys enjoyed by children incorporate electronics and PCBs for their sophisticated functionality.
PCB designers today are challenged to create reliable boards that perform increasingly complex functions while controlling costs and shrinking in dimension. This is especially critical in applications such as smartphones, drones, and other applications where weight is a critical consideration in the PCB characteristics.
Gold is an important element in the design of printed circuit boards, and looking closely at most PCBs will reveal that the ‘fingers’ on the board include metal contacts fabricated from gold. These fingers are typically multi-layered metals that may include materials such as tin-lead, cobalt, or nickel, plated with a final layer of gold. These gold contacts are critical to the functionality of the resulting PCB, establishing the connection with the product containing the board.
Why Use Gold?
Attributes of gold make it an excellent choice for use in PCB fabrication. Edge connectors plated with gold provide a consistent surface finish for applications that are subjected to high-wear such as board insertion edge points. Hardened gold presents a stable surface quite resistant to wear from such repeated activity.
By its very nature, gold is ideally suited for electronics applications:
- It is easily formed and manipulated for connectors, wires, and relay contacts
- Gold conducts electricity very efficiently (an obvious requirement for PCB applications)
- It can carry small amounts of current, essential for today’s electronic devices
- Other metals can be alloyed with gold such as nickel or cobalt
- It does not tarnish or corrode, making it a reliable connection medium
- Melting and reclaiming gold for reuse is a relatively simple process
- Only silver and copper provide higher conductivity properties, but each of them are prone to corrosion, generating current resistance
- Even thin applications of gold can provide reliable and stable contacts with low resistance
- Gold connections can tolerate high temperatures
- Variations in thickness can be utilized to meet the requirements of specific applications
Nearly every electronic device contains some level of gold in its construction including televisions, smartphones, computers, GPS units, and even wearable technology. Computers are natural applications for PCBs containing gold and other gold elements due to the requirement for reliable, high-speed transfer of digital signals more suited to gold than any other metal.
Gold is unrivaled in its for use in applications that include requirements for low voltage and low resistance, making it ideal for PCB contacts and other electronic applications. Usage of gold in manufacturing for electronic devices has now far surpassed the consumption of the precious metal in jewelry fabrication.
Another contribution that gold has made for technology is in the aerospace industry. With the long life expectancy and reliability of gold connections and PCBs integrated into spacecraft and satellites, gold is the natural choice for critical components.
Other Considerations for Gold in PCBs
Of course there are drawbacks to using gold in PCBs:
- Price – as a precious metal there are limited resources of gold, making it an expensive material for use in millions of electronic devices.
- Lost resources – one example is the use of gold in such modern devices as smartphones. The majority of smartphones are not recycled, making careless discarding of the phones a permanent loss of a minute quantity of gold. Although small amounts, the huge volume of discarded devices adds up to a considerable quantity of unrecycled gold.
- Gold applied by itself can be susceptible to wear and smearing under repeated or high-pressure installation/sliding conditions. This makes application over a compatible under-layer utilizing harder materials most effective. Another consideration for PCB use is the combination of gold with another metal such as nickel or cobalt to form an alloy referred to as ‘hard gold’.
- The US Environmental Protection Agency (EPA) has reported that electronic waste is growing at a rate faster than nearly every other waste commodity. This includes not only the loss of gold, but other precious metals and possible toxic materials, as well.
PCB manufacturers must weigh their use of gold in PCB fabrication carefully: applying too thin a layer of the metal may result in boards that fail or are not consistent in performance. Utilizing extra thickness becomes wasteful and expensive for manufacturing.
There are currently very limited choices or alternatives available to PCB manufactures that live up to the capabilities and inherent attributes of gold or gold alloys. Even with the high value of this precious metal it will undoubtedly remain the material of choice for PCB construction.